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Solve $x^{2} + 7 x = 7$ and give your answer correct to two decimal places.

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0.89 and −7.89

0.88 and −7.88

0.89 and −7.88

0.89 and −8.89

answer is B.

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Detailed Solution

Given equation

x^{2} + 7 x = 7

\Rightarrow x^{2} + 7 x - 7 = 0

For the calculation we use quadratic formula we have

x = \frac{- b \pm \sqrt{b^{2} - 4 ac}}{2 a}

a = 1, b = 7, and c = - 7

, (from given equation)
Put the value in the formula we get,

x = \frac{- 7 \pm \sqrt{49 + 28}}{2 \times 1}

\Rightarrow x = \frac{- 7 \pm \sqrt{77}}{2}

\Rightarrow x = \frac{- 7 \pm 8.77496}{2}

[

\sqrt{77} = 8.77496]

x = \frac{- 7 + 8.77496}{2} = 0.88

And

x = \frac{- 7 - 8.77496}{2} = - 7.88

Hence the required value is

0.88

and

- 7.88

.
Correct option is 2.

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